This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. This O-GlcNAc posttranslational modification is highly dynamic and draws comparisons with protein phosphorylation as a biological control mechanism. It has been implicated in gene transcription, nuclear trafficking, protein translation, signal transduction, the regulation of protein-protein interactions, and the sensing of nutritional levels within the cell. Dysregulation of O-GlcNAc contributes to the aetiology of important human diseases, particularly diabetes and neurological disorders. Unlike phosphorylation for which a wide range of pan- and site-specific phospho-antibodies are available, studies of O-GlcNAc modification are hampered by a lack of effective tools for its detection, quantification, and site localization.